The shift gates known hitherto according to the state of the art have corresponding recesses for gear limitation, i.e., for setting the exact position of the shift selector lever within the shift gate, so that the position of the shift selector lever is always limited or defined. In the more recent shift selector levers known according to the state of the art, this gear limitation is sometimes eliminated, especially if the transmission is designed as an automatic transmission and a “tip shifting actuation” is used. With this the driver can manually downshift and upshift the gears by means of the tipping gate. The “tip shifting” thus embodied applies a ground potential to the input of the control device during the actuation of the corresponding tipping button or of the corresponding tip switch. The tip switches of the “tip shifting” are, in general, first sensor elements, which, designed as Hall elements or Hall position transducers or Hall switches, are provided in the shift cover and can be actuated or triggered by a first signal transmitter, which is preferably designed as a permanent magnet. It is problematic here at first that these first sensor elements designed as Hall position transducers cannot be optimally diagnosed at present, i.e., it is not always possible to optimally determine whether these are also able to function at a given moment, so that the corresponding gear limitation, i.e., the recesses in a shift gate which were mentioned in the introduction, cannot always be done away with for safety reasons.
To prevent this problem or to solve this problem, several sensor systems for control device have been known from the state of the art and, in particular, a control device is described in the yet unpublished Patent Application DE 199 38 528, in which a “dynamic diagnosis” takes place when the shift selector lever is moved outside the position “M” for manual shifting, namely, outside the tipping gate. Hall position transducers are provided for this purpose for the first and second tip switches as well as for position “M” between the first and second tip switches, which can be correspondingly triggered with a first signal transmitter, which is associated with a shift selector lever and is designed as a permanent magnet. In addition, a second permanent magnet is provided as a checking magnet. An evaluating circuit provided separately with a sequence generator generates the corresponding signals here based on the checking signals applied. At the moment at which all Hall position transducers are detected as being satisfactory, namely, the corresponding frequency pattern is present, the shift selector lever can then be engaged from the Forward position (E) into the position “M” for manual shifting. If the corresponding frequency pattern is not present after the “dynamic diagnosis” of all Hall position transducers, it is detected that at least one Hall position transducer or a control line associated with that Hall position transducer is not functioning satisfactorily and an acoustic and/or optical warning signal is generated for the driver before engaging the selector lever in position “M” for manual shifting to indicate that the manual shifting actuations do not function.
On the one hand, the above-described “dynamic diagnosis” of the prior-art control device or of the sensor system being described here is not yet optimal, and, on the other hand, it is disadvantageous or problematic that the drivers of the motor vehicles tend to rest their hand on the shift selector lever while driving the motor vehicle. As a result of this, it may happen that the shift selector lever is slightly displaced, i.e., e.g., from the Forward position (E) into the Neutral position (N) or even from the Neutral position (N) in the direction of the Reverse position (R). This means that the shift selector lever will thus assume an “intermediate position” between the Forward E, Neutral N and Reverse R positions actually defined. This may be unfavorable from the viewpoint of safety engineering, because the control device for embodying the corresponding shifting states of the transmission which are desired by the driver in this situation no longer receives any signals any more for the “intermediate position” engaged by the shift selector lever at all, because it is not reported to the control device that the shift selector lever is engaged in position “N,” i.e., in the neutral position, or in position “R” for reverse, i.e., the control device cannot always detect the exact position of the shift selector lever at every point in time.